Inertial reel assembly for a safety belt

ABSTRACT

An inertial reel assembly for use with a safety belt. The reel assembly includes a spindle portion rotatably mounted within a housing for take up and pay out of the safety belt. The spindle is formed with plurality of teeth which engage and lock with the plurality of teeth formed within the interior of the housing. The spindle is mounted to move along an arc passing through its center point so that the spindle teeth may lock with the housing teeth. The housing teeth may include a flat section formed at the tips of the housing teeth for preventing the engagement of the spindle teeth with corresponding housing teeth when the spindle teeth are angularly misaligned with respect to the housing teeth.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The invention relates to an inertial reel assembly for a safety beltwith a rotatably mounted spindle for taking up and paying out the beltwhich is to be drawn out against the force of a spring, comprising atleast one sensor device, which responds to a rate of vehicledeceleration above a certain value, the spindle preferably bearing teethat both ends and performing a translatory or pivotal movement forlocking so that the spindle teeth engage housing teeth.

SUMMARY OF THE INVENTION

Such a safety belt inertial reel assembly is for instance described inthe German patent publication 3,418,378 A. Tn the case of this knowninertial reel assembly the base plate of the mechanism is permanentlyattached to a limb of a frame. A journal serves as a pivot for anoperating disk. The spindle, which is supported in this operating disk,is furthermore permanently connected with an operating wheel. If now oneof the sensors provided is triggered, the operating wheel is latched tothe operating disk by a pawl. If more belt is paid out, the operatingdisk will now turn with the spindle about the journal and the teeth onthe spindle will come into engagement with the housing teeth in thelimbs of the frame. In the case of this known belt take up assembly,angular alignment during engagement movement with respect to the teethconnected with the housing is ensured owing to the locked state of theoperating wheel in relation to the operating disk.

In use it may happen that shortly before an accident the operating wheelis in a position in which triggering of a sensor would mean that thecorresponding pawl would so drop onto the back of a tooth and so engagethe operating wheel that the spindle has to turn through one tooth pitchbefore the operating wheel is locked. In the case of a sudden, jerkedpaying out of belt as occurs in the case of a crash, the great inertiaof the spindle will mean that the spindle will be more rapidly jerkedupwards so than it is turned the corresponding amount. The consequenceis angular misalignment during engagement with the housing teeth. Inthis respect it may happen that the spindle teeth are not completely inalignment with the teeth connected with the housing and in an extremecase, although the known reel just keeps to requirements, it only doesso marginally.

Therefore the object of the invention is to achieve a complete overlapof the spindle teeth with the housing teeth even in this extreme case ofangular misalignment of the spindle and thus to provide for thetransmission of a great force.

This object is achieved since the housing teeth have flats, whichprevent a coming into engagement of the spindle teeth in the angularlymisaligned state. In accordance with a preferred embodiment of theinvention the spindle is so supported that on coming into engagementwith the housing teeth it pivots about a point fixed in relation to thehousing, which is on a circle about the center point of the spindle inits inactive position and having a radius equal to the pitch circlediameter. In the case of a positioning of the housing teeth wherein thecenter of the housing teeth is located on a line drawn through thecenter point of the spindle in its engaged position, which line itselfis perpendicular to the line connecting this center point with the pivotpoint of the spindle, it is possible for the part, which bears theteeth, to be largest so that the force may best be transmitted from thespindle to the sheet metal frame. The first tooth of the set of housingteeth has to be so positioned that the spindle is able to turn withoutobstruction in its neutral condition and even in the case of a minimumpivoting angle does not immediately come into engagement with thehousing teeth. The last housing tooth has to be so arranged that thespindle is still able to swing freely into and out of engagement. Thefirst third of the housing teeth has a flat. If the spindle is jerkedupwards in the angularly misaligned state, the spindle teeth will landon the flats of the housing teeth and engagement is prevented. Were itnot for these flats in accordance with the invention the spindle wouldengage even starting from this angularly misaligned state and the loadwould only be transmitted to the last housing teeth. In the case of avery high load this may lead to stripping of the last teeth and thus tothe spindle slipping. However on the other hand in the case of the teethin accordance with the invention the spindle is prevented by the flatsfrom making misaligned engagement. In the case of further paying off ofthe belt the spindle teeth will slide so far onto the flats of thehousing teeth that an angularly aligned position is reached. In order inthis case as well to prevent the spindle from hooking onto the lasthousing teeth, these teeth as well have flats. When the angularlyaligned position is reached and the spindle is still under load, it willcome into complete engagement. The force may now be transmitted over theentire teeth from the spindle to the sheet metal frame.

It is an advantage if the spindle teeth are so designed that they alsohave flats, which are aligned with tip circle of the spindle. This makesit possible to effect better sliding on the flats of the housing teeth.This is also the possibility of making the angle of the housing teethsmaller than the corresponding angle of the housing teeth. This meansthat during engagement there will be some play between the two sets ofteeth so that the time, which is available for the engagement of theteeth, is prolonged. In the case of a particularly advantageous designin accordance with the invention the housing teeth are offset by halfthe tooth pitch on the two sides of the sheet metal frame. The sheetmetal frame is so designed that the teeth or the entire limb may readilydeform under toad. When, as normally the case, the spindle is lifted atboth ends, it will come into complete engagement at that end, at whichits teeth are nearest to the aligned position. On further tension thesheet metal frame or the teeth will deform to such an extent that theother end will come into the aligned position and will also engage. Ifhowever the spindle is unevenly lifted, for instance owing to obliquepull on the belt, so that it will engage first at one end, in the caseof a symmetrical arrangement of the housing teeth the spindle teeth onthe end with the lag would already be past their aligned position andthe end with the lead would have to be deformed by an entire tooth pitchbefore the second end could engage. Owing to the offset by half thetooth pitch there will be--even in the limiting extreme--a deformationby one half of the tooth pitch takes place. Therefore engagement at bothends to completely transmit the load is ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to thedrawing.

FIG. 1 shows a conventional spindle and housing tooth system in thecourse of engagement starting from an angularly misaligned position.

FIG. 2 shows the spindle and housing tooth arrangement in accordancewith the invention in the neutral position.

FIG. 3 shows the spindle in accordance with FIG. 2 with angularmisalignment and attempted engagement.

FIG. 4 shows the spindle in accordance with FIG. 3 after furtherrotation and further pivoting.

FIG. 5 shows the teeth on the spindle and the housing as in FIGS. 2through 4 in the angularly aligned position and shortly before finalengagement of the teeth.

FIG. 6 shows the teeth on the spindle and the housing in fullengagement.

DESCRIPTION OF THE DRAWINGS

FIG. 1 serves to show an inertial reel assembly in which a spindle, 20for a coil of safety (not shown) belt is supported for rotation againstthe force of a spring 22 about the pivot point 1. A spindle disk 2 islocked in rotation with the spindle 20 and it bears spindle teeth 3. Acutout 5 is provided in the sheet metal frame or housing 4 having abackwall 4a to receive the disk 2 with the teeth 3 thereof so that itmay freely rotate about its axis 6 in the neutral position. The backwall 4a of the housing is at least partially cut away to form limbs 24and at least one sensor device 26 which responds to a rate ofdeceleration above a certain value is cooperatively connected to theassembly in a conventional manner to activate the assembly. The teeth 7of the housing 4 are of conventional design. If now the spindle ispivoted with angular misalignment towards its locked position it ispossible for the condition illustrated in FIG. 1 to arise. In the part Aof the teeth 7 on the housing the spindle teeth 3 have already movedpast the tooth tips. In the part B of the housing teeth 7, on the otherhand, the spindle teeth 3 have not yet reached the tips of the housingteeth so that at this instant there is merely one engagement at thehousing tooth 8. When further safety belt is paid out, which compelsfurther movement in the engagement direction of the spindle, the spindletooth 8 will deform to such an extent that in an extreme case the twofollowing teeth will engage with the spindle teeth. If now a very highload occurs, which is not able to be resisted by the teeth which are inthe engaged condition, the first thing to happen is that the tooth 8will be stripped. Although then the next tooth will come into engagementwith the spindle teeth, the load will however only be transmitted bythree of the housing teeth 7 at the most. As a result of this the teethon the housing will be stripped off one after the other and the spindlenot be held.

In the figures the teeth arrangement in accordance with the invention isillustrated taking into account the same functional principle as inFIG. 1. In FIG. 2 the neutral position of the spindle is illustrated.The spindle disk 2, which bears the spindle teeth 3', is able to freelyrotate about its axis 6 when the belt is paid out and taken up. Theteeth 11 through 14 of the housing are in this case provided with flats15. Furthermore each of the spindle teeth 3' are provided with flats 16,the flats 16 themselves tangentially aligned with a tip circle 10radially defined from spindle axis 6 to the flats 16 at the tip of eachof the spindle teeth.

In FIG. 3 the spindle is shown jerked upwards in the angularlymisaligned position. In this case it has been pivoted along the circularpath 9 about the point 1 till the flats 16 of the spindle teeth 3'engage the flats 15 of the housing teeth 11 and 12. The flats 15 areexactly on the tip circle 10 shown in broken lines of the spindle teeth3' in this position. Therefore the spindle is prevented from pivotingfurther about the point 1. Furthermore the teeth 13 and 14, past whichthe spindle teeth have not yet moved in the illustrated position, areprovided with a flat 15 so that in this case it is not yet possible forthe teeth to engage. The exact form of the flat 15 on the teeth 13 and14 will be seen from FIG. 4. The spindle has in this case been furtherturned to such an extent that the part of the spindle teeth, which inFIG. 3 is adjacent to the flats of the teeth 11 and 12, has already runpast the same and it is possible for the spindle to pivot further alongthe path 9 a small distance. The flats 15 of the teeth 13 and 14 willnow be on the tip circle 10' shown in broken lines, of the spindle inthis position. On further rotation of the spindle in FIG. 5 these flats15 of the housing teeth 13, 14 are passed by the spindle teeth and thespindle will reach its angularly aligned position. It is now possiblefor the spindle to pivot further about the point 1 in FIG. 6 forcomplete engagement with the housing teeth 7'.

In this condition the load, which acts on the spindle, will betransmitted by all teeth to the sheet metal frame. The flankstransmitting the load of the spindle and housing teeth are slightlyundercut to an angle in a range of about 0° to 15° on their lockingflanks as shown in FIG. 6 by numeral 28 in order to prevent the spindleteeth being forced by a very high load out of engagement with thehousing teeth and on the other hand to ensure that on pivoting into theengagement position the spindle teeth reliably come into engagement withthe housing teeth.

I claim:
 1. An inertial reel assembly for a safety belt with a spindledisk rotatably mounted within a housing for taking up and paying out abelt which is to be drawn out against the force of a spring, saidspindle disk having a center point, and said inertial reel assemblycomprising at least one sensor device which responds to a rate ofvehicle deceleration above a certain value, the spindle disk bearingteeth and performing a translatory movement along an arc passing throughthe center point thereof to a locking position so that the spindle teethengage a plurality of teeth formed in said housing, characterized inthat one or more of said plurality of said housing teeth include a flatsection at the tip of said housing teeth for preventing engagement ofsaid spindle teeth with said housing teeth when said spindle disk haspivoted along said center point to translate said spindle disk alongsaid arc so that said spindle teeth are angularly misaligned withrespect to said housing teeth, wherein said spindle teeth are formed asblunt teeth, and flat sections are formed on the tip circle of the bluntteeth.
 2. The inertial reel assembly for a safety belt as claimed inclaim 1, characterized in that during engagement with the housing teeththe spindle disk pivots about a point fixed in relation to the housing,such point being on a circle about the center point of the spindle diskwhen said spindle is in a neutral position, said circle having a radiusequal to a pitch circle diameter of said spindle disk.
 3. The inertialreel assembly for a safety belt as claimed in claim 2, characterized inthat said housing teeth are formed along a circle defined by a center,said center lying on a line drawn through said center point of saidspindle disk when said spindle disk is in an engaged position, said lineperpendicular to the line connecting said center point with the pivotpoint of the spindle disk.
 4. The inertial reel assembly for a safetybelt as claimed in claim 3, characterized in that the housing teethbegin approximately 20° from the pivot point in the direction of windingup the safety belt.
 5. The inertial reel assembly for a safety belt asclaimed in claim 3, characterized in that the plurality of teeth formedin the housing includes a last housing tooth with which the spindleteeth may engage, said last housing tooth including a non-locking flankportion, which makes an angle of not less than 90° with a lineconnecting the pivot point of the spindle disk with a point on saidhousing tooth flank which simultaneously constitutes a point on the rootcircle of the housing teeth.
 6. The inertial reel assembly for a safetybelt as claimed in claim 5, characterized in that the root circle of thehousing teeth is on the tip circle of the spindle disk teeth when thespindle disk is translated inwardly towards the housing and in that atleast the base of the housing teeth has a configuration adapted to theteeth of the spindle disk.
 7. The inertial reel assembly for a safetybelt as claimed in claim 6, characterized in that the angle formed by aback portion of each of the spindle teeth which engages correspondinghousing teeth is smaller than a corresponding angle of the housingteeth.
 8. The inertial reel assembly for a safety belt as claimed inclaim 1, characterized in that approximately a first third of thehousing teeth has a flat section, which is located on the tip circle ofthe spindle teeth when the spindle disk is translated inwardly to engageapproximately the first third of the housing teeth with the spindleteeth.
 9. The inertial reel assembly for a safety belt as claimed inclaim 8, characterized in that some of the remaining two-thirds of thehousing teeth also has a flat section, each flat section located on thetip circle of the spindle teeth when the spindle disk has beentranslated inwardly along the arc to a point where there is still roomfor a small degree of inward translatory motion until said lockingposition is reached, said some of the remaining two-thirds housing ofsaid housing teeth being those teeth whose tips come into engagementwith the spindle teeth just short of said locking position upon furtherinward translatory motion of said spindle disk.
 10. The inertial reelassembly for a safety belt as claimed in claim 9, characterized in thatthe spindle teeth have undercuts in the range of 0° to 15° on theirlocking flanks.
 11. The inertial reel assembly for a safety belt asclaimed in claim 9, characterized in that the spindle teeth are formedas blunt teeth, and the flat sections are formed on the tip circle ofthe blunt teeth.
 12. The inertial reel assembly for a safety belt asclaimed in claim 1, further comprising means for subjecting the housingto an elastic deformation after said spindle disk is positioned forengagement to permit further rotation of the spindle disk in thedirection of payout of the safety belt through an amount equal to thelength of one tooth.
 13. The inertial reel assembly for a safety belt asclaimed in claim 12, characterized in that cutouts are provided in aportion of the sheet metal frame covering the housing teeth and saidcutouts allow a displacement of the housing teeth in relation to saidsheet metal frame when said housing teeth are subjected to a load. 14.The inertial reel assembly for a safety belt as claimed in claim 12,characterized in that one or more limbs of the sheet metal frame areattached to a back wall of the housing, to permit a slight bending ofthe limbs of the frame in relation to a back wall of the housing whensaid housing teeth are subjected to a load.
 15. The inertial reelassembly for a safety belt as claimed in claim 12, characterized in thatthe spindle teeth on one side of the spindle disk are offset by half thetooth pitch in relation to an opposed side of said spindle disk.
 16. Theinertial reel assembly for a safety belt as claimed in claim 12,characterized in that the housing teeth on one side of the housing areoffset by half a tooth pitch in relation to any opposed side of thehousing.